Hand drill and drill press

ABSTRACT

The invention contemplates a miniature drill which is hand-held at a quill or sleeve on the drill axis, in the manner of a pencil or pen. The tool includes mass eccentric to the drill axis for absorbing reaction torque occasioned by drill operation. In one employment, the fingers of the hand which holds the sleeve also steady the drill against the workpiece, and in another employment a work-supporting jig fastened to the sleeve converts the tool into a portable miniature drill press, assuring accurate tool alignment upon entering and through a drill-feeding stroke into the work.

United States Patent Von Hollen 5] Feb. 8, 1972 [54] HAND DRILL AND DRILL PRESS [72] Inventor: John Von Hollen, PO. Box 185, Cedar Grove, NJ. 07009 [22] Filed: Feb. 24, 1970 211 Appl. No.: 13,472

[52] US. Cl ..408/l01, 173/163, 408/97 [51] Int. Cl ..B23b 45/14 [58] FieldofSearch ..408/97, 101,202,203, 137

[56] References Cited UNITED STATES PATENTS 2,499,65 8 3/1950 Livingston .408/ l 01 Rumuau mm mm Mm ma.

Primary ExaminerFraneis S. Husar Attorney-Sandoe, Hopgood and Calimafde [5 7] ABSTRACT The invention contemplates a miniature drill which is handheld at a quill or sleeve on the drill axis, in the manner of a pencil or pen. The tool includes mass eccentric to the drill axis for absorbing reaction torque occasioned by drill operation. In one employment, the fingers of the hand which holds the sleeve also steady the drill against the workpiece, and in another employment a work-supporting jig fastened to the sleeve converts the tool into a portable miniature drill press, assuring accurate tool alignment upon entering and through a drill-feeding stroke into the work.

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/ ATORNEY HAND DRILL AND DRILL PRESS This application relates to a miniature hand drill and handdrill press for drilling, reaming and other cutting operations.

Portable drills incorporating their own electric motor or other drive are common and valuable tools. In smaller sizes, they employ a pistol grip or other means of manual grasp. However, when using such drills for the smaller drill-bit sizes, problems arise from lack of balance, and from off-axis motorreaction torque, with the result that the drill-bit may be broken or may skid over the work, as control over the desired drill-bit alignment is momentarily lost. Such problems become more acute when the work to be drilled presents a convex surface.

It is, accordingly, an object of the invention to provide a miniature-drill construction which substantially avoids the above-noted difficulfies.

Another object is to provide a miniature hand drill which is compact is size, well balanced and simple to operate.

It is a further object to provide a miniature hand-operated drill which is easy to control, simply made and economical, and yet quite versatile in its use.

It is a still further object to provide a novel drill press which facilitates the manual drilling of materials, including the convex surface of a small workpiece, such as a ball or rod, in a highly accurate and easily controllable manner.

It is a still further object to provide a portable miniature drill-press attachment which is readily assembled to a portable miniature drill.

It is still another object of this invention to provide a fixture for holding a miniature tool and workpiece in portable, yet precisely aligned operative relationship with one another.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following description taken in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred embodiments of the invention:

FIG. 1 is a perspective view of a miniature drill made of the invention, with its associated power supply;

FIG. 2 is an exploded perspective view of the miniature drill of FIG. 1;

FIG. 3 is an enlarged fragmentary sectional view of the miniature drill and a tool bit held therein;

FIG. 3A is an enlarged perspective view of a flanged collar forming part of the chuck mechanism in the drill of FIGS. 1 to FIG. 4 is a schematic representation of the electrical connections for the drill of FIGS. 1 to 3, including a sectional view of the ring-contact portion thereof;

FIG. 5 is a sectional view of a modified finger rest for precise control of the drill according to the invention;

FIG. 6 is a force diagram to illustrate an operating feature of the invention;

FIG. 7 is an exploded perspective view of a drill press made according to the invention;

FIG. 8 is a sectional view of another drill press according to the invention;

FIG. 9 is a perspective view of a workpiece-retaining plate or shield used with the drill presses of FIGS. 7 and 8;

FIG. 10 is a sectional view of another shield usable with the drill press of the invention;

FIG. 11 is a perspective view of the miniature drill to illustrate its use as a circle cutter;

FIG. 12 is a perspective view of a fixture according to the invention, shown for application of my invention to the drilling of a small diameter shaft on a relatively large assembly;

FIG. 13 is a perspective view of a combined workpiece holder and tool holder, forming a part of the fixture of FIG. 12;

FIG. 14 is a sectional view of the fixture of FIG. 12, taken along line l4--l4 of FIG. 12;

FIG. 15 is a view in elevation, partly broken-away and in section, showing a fixture of the invention, embodying a workpiece-surface locator;

FIG. 16 is a fragmentary view in elevation, partly brokenaway and in section, to show modification of part of the fixture of FIG. 15.

Briefly stated, the invention contemplates a miniature drill which is hand-held at a quill or sleeve on the drill axis, in the manner of a pencil or pen. The tool includes mass eccentric to the drill axis for absorbing reaction torque occasioned by drill operation. In one employment, the fingers of the hand which holds the sleeve also steady the drill against the workpiece, and in another employment a work-supporting jig fastened to the sleeve converts the tool into a portable miniature drill press, assuring accurate tool alignment upon entering and throughout a drill-feeding stroke into the work.

Referring to FIG. 1, the invention is shown in application to a miniature portable drill 10 having a quill or sleeve 11 by which it is manually grasped and manipulated; conveniently, the sleeve 11 may be of plastic, such as polyethylene. A flared outer end 12 enables a finger grip, in the manner of a pen or pencil, close to the working region of an axially projecting drill bit 13 or other tool element, as needed. The sleeve 11 is assembled with other nonrotating tubular structure 14 connected to a rearwardly projecting motor housing 15. A flexible cable 16 connects the motor to a powerpack 17 which normally is placed on a nearby bench, in order that the tool mass to be manipulated may be kept to a minimum. Preferably, the motor 18 (FIG. 2) within housing 15 is DC operated, and adjustable means 19 forming part of the power supply 17 provides convenient selection of voltage, and thus speed, for the motor 18. An On-Off switch control 20 is shown on the motor housing 15, for a purpose to be later explained, and a selector switch 21 and a polarity-reversing switch 22 are shown at the powerpack 17.

It is a feature of the invention that the drill shall be grasped and manipulated by way of the sleeve or quill 11 and that the mass of the motor and its housing shall not only be rearward of the sleeve 11 but also eccentric to the sleeve axis, which is also substantially the axis of the drill bit 13. The motor 18 is preferably capable of relatively high rotational speeds, and mechanical advantage is developed through reduction gearing 23-24, from the motor-output shaft 25 (FIG. 3) to a drill drive-shaft 26. The reduction gearing provides a means of conveniently offsetting the motor mass with respect to the drill-bit axis.

As shown, a circular base 27 provides rugged support for bearings 28-29 for the shaft 26. The base 30 of motor 18 is ruggedly offset from base 27, by spacer feet 31, thus defining a region 32 for accommodation of the gearing 23-24 and switch 20. A thrust bearing 33 referenced to the motor base 30, sustains the axial component of the drill load.

Various drill bits or other tool elements 13 are selectively held in an elongated chuck 34, within sleeve 11. Chuck 34 may be a conventional dental chuck, and therefore a simplified showing will suffice. As shown, plural chuck jaws 35-36 are carried at the end of shaft 26. The outer profile of these jaws lies in a gradually flaring cone; the jaws being poised for radially inward jamming against the reduced shank 37 of the drill bit 13 whenever a chucking sleeve 38 is driven (to the right in the sense of FIG. 3). The chucking sleeve 38 pilots on shaft 26 and is axially between clutch-shifting shoulders 39-40. The shoulder 39 forms part of an elongated tubular barrel 41 having limited freedom to slide axially in the bore of a bushing 42; a flange 43 on bushing 42 is the means of secure mounting to the base 27 and the elongated bearing 29 is longitudinally guided in the counterbore 43 of barrel 41. Key means 45 tracks elongated slots or ways 46 in bushing 42, and a compression spring 47 normally urges the parts to the chucking relation shown. An angular ofiset 48 (FIGS. 2 and 3A) near the end of slots 46 will receive keys 45, upon slight angular rotation of barrel 41, for selective holding of an provide a clean forward end, with a reduced aperture 51 by which to guide the insertion of a drill-bit shank 37. The quill or manipulating sleeve 11 is tightly fitted over the substantial length of the inner sleeves 41-49. Unchucking is accomplished by grasping the quill 11 and urging the same, against spring 46, toward the motor housing 15. This relieves shoulder 39 from the chuck shifter 38 and allows the latter to float rearwardly, once freed (by shoulder 40) from jaw contact. The unchucked condition may be retained at 45-48 until the bit 13 has been replaced, whereupon disengagement at 4548 will permit spring 46 to reset the chuck on the new bit. Of course, if unbiased chuck action is desired, the spring 46 may be omitted.

As a feature of the invention, a fingertip control switch is incorporated within the flared end of the quill 11. This switch relies upon resilient radially compliant suspension of a thin flared annular ring 55 of conducting material; the yielding nature of the plastic rubber or the like material of quill l 1 will be understood to provide said suspension. Ring 55 has an outer contour to determine flared support for the end of quill 1 1. Its inner contour conforms to that of the rounded end of sleeve 49, and it is positioned in relatively close radial clearance therewith by an insulating ring 56 of readily yieldable material; ring 56 may conveniently be a Neoprene O-ring. Registering annular grooves (57, in the bore of ring 55, and 58, in the curved end of sleeve 49) provide adequate axial retention of the ring 55, once assembled by snap action after quill 11 is fitted over the tubular members or sleeves 41-49. If desired, tap, shoes 59-59 of conductive material may line the bore of ring 55 adjacent O-ring 55, to provide reduced radial clearance to be closed by finger grasp in order to complete an electric switch circuit from ring 55 to sleeve 49.

FIG. 4 is a simple electrical diagram to show that the fingergn'p switch 55-49, just described, may be optionally employed, depending upon selective positioning of the On-Off switch 20. In the position shown, switch 20 completes its circuit to ground (sleeves 41-49) via contact 60, insulated flexible conductor 61, and the conductive sleeve 55, whenever the flared end 12 is sufficiently squeezed; a similar insulated flexible conductor (not shown) will be understood to complete ground connections from sleeve 41 to the motor ground 62.

FIG. 4 also illustrates that the switch 21 shown (in FIG. 1) located at the powerpack, may provide selective supply of plural voltages to the motor 18. The power supply may be a rectifier operated from house wiring, but in FIG. 4 the power supply is schematically indicated by a battery 63 having a center top, by which switch 21 may selectively detemiine increased voltage supply to the motor, as for use with very small drill-bit diameters.

Finger manipulation and controllability of the drill of FIGS. 1 to 4 may be enhanced by the arrangement depicted in FIG. 5, wherein the conductive nose switch element 65 replaces that shown at 55 in FIGS. 3 and 4. Element 65 is shown as cupshaped, to fit over the nose of chuck element 49 and to be poised, by compliant suspension from quill l l, in slight radialclearance relation (at 66) and axial-clearance relation (at 67) with the nose of chuck element 49; if desired, a resilient O- ring 68 (suggested by phantom outline, at the bottom of the counterbore of element 65) may provide more positive retention of such clearances 6667, depending on the stiffness of quill 11 and the preference of the user. A radial flange 69 forms part of the element 65, and the nose end of the quill is stretched over flanger 69 to define an air-backed region 70 of comfortable adaptability to finger grasping. The cushion effect thereby achieved is found to absorb motor and/or toolworking vibrations, as well as inertial forces resulting from changing motor speed.

In manual use, the entire drill is grasped at quill 11, in the manner of a pen or pencil, i.e., as by using the thumb, forefinger and middle finger at roughly l20-spaced locations about the quill axis. The forefinger and middle finger, being longer than the thumb, naturally engage quill 11 at the nose end, i.e., at the flare 12 (region of element 55, in FIG. 3; re-

gion of cushion 70 and flange 69, in FIG. 5), and the thumb naturally engages quill 11 at a location rearward of the noseswitch elements. Quill orientation stabilizes still further rearwardly be resting against the side of the hand, between thumb and forefinger, and at the root of the forefinger. Under these circumstances, a light grip will be insufficient to close the nose-switch elements (5549, or 65-49) thus establishing a power cutoff condition, but a slightly greater squeeze of the thumb against the forefinger and middle finger will complete the circuit to drive the drill, in accordance with the polarity and magnitude settings previously selected at 21-22. The ring finger and little finger remain available to stabilize the handheld reference of the drill to a table or other surface in the immediate vicinity of the working region of the drill bit.

It has been previously indicated that the radially offset relation between the motor mass and the quill axis represent a feature of the invention. Desirably and naturally, the drill is grasped as shown in FIG. 1, with the predominant mass of the motor and its housing 15 pendulously suspended below the quill axis, and the force diagram of FIG. 6 depicts the reaction to a speed change, such as a motor start. In FIG. 6, the chuck or quill axis is designated C, and the point CG identifies the center of gravity of the motor and its housing 15, which may be substantially coincident with the motor-shaft axis. The radial offset L is thus defined, between C and CG. For any motor speed change, such as a motor start, a reaction torque will tend briefly to rotate the motor housing 15 and, with it, the drill chuck, thus producing a jerking efi'ect. However, the offset L, represents a pendulous suspension so that the suspended mass Wof the motor and its housing is available to partially compensate for or offset the severity of start-stop reaction torques. Specifically, the force W will normally act downwardly at the point CG, and the start-reaction torque will produce a transient angular displacement 0 about the drill-bit axis C, thus displacing to a laterally offset point 71 the location at which force Wacts with respect to the hand-held axis. Pendulous reaction to this lateral offset D will introduce a restoring counter-torque Tin accordance with the relation:

T=WL sin 0 For larger offsets of the point CG, as for the offset L for CG, the lateral displacement to point 71 for the angle 6 will establish correspondingly greater restoring torques; or, stated in other words, at such larger offsets (L), the transient angular deflection upon starting will involve a smaller angle (about C) for the same lateral displacement D. It will be appreciated that in use, the tool operator may find a convenient grasping technique to suit his personal preference, whereby, for example, the force W is given a laterally biased offset (as to the extent D) prior to starting, so that motor-start reaction torque will encounter still greater pendulous restoring action T, due to the larger values of sin 0 which will necessarily be involved.

Quite aside from the described features of the invention for manually held operation, the invention has particular and further utility in conjunction with various miniature drill-press configurations, illustrated in the remaining figures. In the arrangements of FIGS. 5 to 10, the drill 10 is chucked to an elongated shank or extender for further chuck means 81 in which a drill bit 82 is held, for drilling a radial hole in a workpiece 83, such as a small rod. The workpiece 83 is held by suitable means, as between releasably clamped plates 84-85. The upper plate 85 has a central aperture 86 to receive the drill bit with ample clearance, and one or more V-grooved radial formations 87-87 on the underside of plate 85 enable precise positioning of the workpiece axis, to intersect the axis of aperture 86. Clamp bolts 88 extend through the base plate 84 to engage tapped holes 89 in the upper plate 85, thereby securing the workpiece 83.

Stabilized alignment of the drill bit 82 with respect to the workpiece 83 may be achieved by using a cylindrical support or tube 90 as the connecting reference between clamp plate 85 and the drill l0. Tube 90 may be of glass or rigid transparent plastic, to enable a full view of the drilling operation, and in FIG. 5 tube 90 is seated against a shoulder adjacent the reduced end 91 of plate 85 (see FIG. 9). The upper end of tube 90 may carry suitable adapter means 92 to removably support a head member or annular plate 93, and bolts 94 and tapped holes 95 provide suitable means to secure members 92-93. Plate 93 will be understood to include a central bearing for central piloting alignment of the shank 80 and to include suitable guide formations (not shown) on its lower surface, to locate in the bore 90 of adapter 92. Further stabilizing alignment of the shank 80 is provided by bearing means 98 on a standard or bridge structure 97 which is also secured by the bolts 94. If desired, the described drill press may normally urge the tool 82 away from the workpiece 83, using a spring 99, compressionally loaded between bearing 98 and axially clamped means 100 on the shank 80; a collar 101 clamped to shank 80 beneath plate 93 provides an upper limiting position or stop, governing the tool-retracting action of spring 99.

The arrangement of FIG. 8 is generally similar to that of FIG. 7, except for certain details. The transparent shield 105 is cupshaped rather than merely tubular (90), and with a substantial stifiening body 106 to establish an elongated bearing reference 107 for the shank 80, where it passes through the upper (closed) end of the shield 105. The shield 105 is preferably of plastic an is internally grooved at its lower (open) end for quick detachable snap-acting engagement with a bead formation 108 on work-retaining plate 85. Plural elongated, angularly spaced, radial blades 109 are united to and carried by body member 106 for direct supporting abutment with the upper surface of the plate 85 when in the snapretained assembled position shown. A cylindrical shroud 110 surrounds and protects the spring 99; in FIG. 8, spring 99 is shown retained between locating cups 111-112, being preferably secured to the former and free to slide with respect to the latter. Thrust bearings or washers 113-114 are respectively interposed between cup 1 1 1 and the closed end of shield 105, and between cup 112 and the lower half of dog-clutch means or collar 115 (corresponding to collar 100). In use, the drill will be understood to drive shank 80, and as the drill 10 is depressed to cause tool 82 to enter the work, spring 99 is further compressed as shroud 110 freely telescopes over the collar or clutch element 115. Alternatively, shroud 110 may be axially compressible (e.g., a bellows) with its ends carried by the respective cups 1 1 1-1 12.

FIG. 10 illustrates a modification in which a removable closure member 118 is snap-engaged at its bead 119 to the lower end of the shield 105, i.e., in place of the workpiece clamp structure of FIG. 8. Closure member 118 has a central aperture lined with a ring 120 of firm friction material, such as Neoprene, to enable the drill and press of FIG. 8 to be hand held against a workpiece (not shown).

FIG. 11 illustrates a circle-cutting use of the drill of FIG. 1, requiring only the addition of a removable clamp 121 to the quill, at a selected location therealong, depending on the desired radius of cut. A small circular saw blade 122, clamped to a mounting shank 123, is chucked to the drill 10, and a center" pin 124 projects from clamp 121 to determine the center for cutting the circular arc 125 in the workpiece or sheet 126.

FIGS. 12 to 14 illustrate a form of drill press wherein rotation of an external nut 130 determines feeding advance of the drill bit 131 with respect to a small workpiece 132; these figures also illustrate that the drill press may be the means of temporarily uniting the drill to the much larger element 133, for purposes of accurately drilling a small part thereof.

Basically, the press of FIGS. 12 to 14 comprises an external sleeve 134, shown alone in FIG. 13, and an internal sleeve 135 having a longitudinally guided sliding fit to the bore of sleeve 134. After removing the quill or jacket 11 (and also the fingerpiece switch means 55 or 65), the internal sleeve 135 is fitted over the projecting end of the clutch shifter 49, and a setscrew 136 is shown holding the parts, thus mounted (see FIG. 14). At the end which telescopically fits the sleeve 135 the outer sleeve 134 is longitudinally slotted, as at diametrically opposite locations I37-137', to provide keyed location of the outer sleeve. As shown, a pair of diametrically opposite projections 138-138 on the inner sleeve 135 have keyed engagement to slots 137137 and project further outward for interception of one axial end of the nut 130, engaged to the threaded end 139 of sleeve 134. On the other axial side of nut 130, diametrically opposite bolts or studs 140-140 are removably carried by sleeve 135 and have a similar relation to the slots 137137 and nut 130. Thus, adjustment of the nut causes variation in the telescoped extent of sleeves 134-135.

At its other end, the outer sleeve 134 is also longitudinally slotted, at 141-141, and aligned V-forrnations 142 terminate both slots 141-141 at the same longitudinal location. Sleeve 134 is also externally threaded at 143, for substantially the extent of slots 141-141, and a clamp nut 144 is removably engageable with threads 143.

In use, the desired part 132 of the workpiece is entered into the slots 14114l', and nut 144 is set to clamp the same against V-formations 142, thereby establishing a secure and well-centered orientation and reference for the bore of sleeves 134-135, with reference to the workpiece. The drill 10 is then started (switch 20), and nut 130 is driven to feed the drill in and through the workpiece; clean retraction of the bit 131 is accomplished when backing-threading the nut 130.

FIG. 15 illustrates use of a router or milling-cutter 150 in a press or adapter tool 151, much of which has already been described in connection with FIGS. 12 to 14, so that the same reference numbers are used, where appropriate. Thus the same means are used to mount tool 151 to the end 49 of the drill. However at its working end, the tool is fitted with a cap 152 threaded at 153 to the outer sleeve, and the flat radial end face 154 of nut 152 serves as a guide or reference to determine the cutting position of tool element 150. Adjustment of the fit at 153 determines depth of cut by element 150.

FIG. 16 illustrates a slight modification, applicable to the forms of both FIGS. 12 to 14 and FIG. 15, whereby the inner sleeve can be dispensed with, by utilizing shifter 49 as the basic guide for the bore of the outer sleeve 134. Thus, the key means -155 for Hacking adjustment of nut 130 may be bolts carried by shifter 49.

It will be seen that a drill and drill press of the invention meet all the stated objectives and provides great facility and accuracy for the performance of small, delicate drilling or other cutting operations. The invention finds utility in many rotary cutting applications including reaming and buffing, and it is applicable for hand-held and jig or press-held situations. Thus, while the invention has been described in detail for the fomrs shown, it will be understood that modifications may be made without departing from the scope of the invention.

What is claimed is:

1. A fixture for holding a tool and workpiece in operative relationship with one another, comprising a tubular workpiece and tool holder having a bore extending therethrough along the tubular axis and having at one axial end a workpiecereceiving slot cut along an axial plane and bottoming at a desired axial location to define opposing workpiece-retaining jaws at the slot bottom, said slot being sized to receive and place a workpiece across the bore between the jaws near the bottom of the slot, said holder further having at the other axial end a tool-guiding slot extending along the holder and bottoming at a desired axial location from the other holder end, said tool-guiding slot having a sufficient axial length for guidance of a tool placed within the bore into operative engagement with the workpiece across the bore, and means for retaining the workpiece into firm engagement with the bottom of the slot.

2. The fixture of claim 1, wherein said workpiece receiving slot bottom is selectively shaped with said jaws converging towards one another at the axial plane, with said workpiece being retained against the converging jaw portions to hold said workpiece symmetrically with respect to the axial plane.

3. The fixture of claim 1, wherein said last-defined means includes a nut threadedly engaged to said tubular holder at the workpiece-receiving end.

4. The fixture of claim 1, wherein said holder includes telescoping inner and outer tubular members at the toolholder end, key means coacting between said members to limit their relative movement to substantially that of axial displacement, and feed means including rotatable member threaded to one of said tubular members and in longitudinally located relation to the other of said tubular members.

5. A fixture for determining the operative relationship between a tool and workpiece, comprising a tubular workpiece engaging and tool holding means having a bore along the tubular axis and externally threaded, the bore of said tubular means at one end being adapted for concentric guided support upon a nonrotafing tubular end of a tool, said tubular means at said end having an elongated key slot for keying the same against rotation with respect to said tubular end of the tool, nut means threaded to said tool holder at the slot region and including means for longitudinally locating the same with respect to said tubular end of the tool, whereby nut rotation adjustably positions the tubular holder with respect to the tool, and work-engaging means at the other end of said tubular means and including a circumferentially continuous member in threaded engagement with said tubular means at said other end.

6. The fixture of claim 5, in which said other end of said tubular means is longitudinally slotted to receive a workpiece, and in which said circumferentially continuous member is a nut engageable with an inserted workpiece to drive the same into tight seating against the inner slotted limit.

7. The fixture of claim 5, in which said circumferentially continuous member is a cap having a threaded bore engaged to threads at said other end of said tubular means, said cap having a central opening at the closed end thereof for reception of a tool element held by said tool.

8. A fixture for determining the operative relationship between a rotary tool and a workpiece, said tool having a rotatable part projecting from a nonrotating part, comprising a tubular body having means at one end for removable attachment to the nonrotatable part of the tool and with the rotatable part projecting within the bore of said body, a sleeve at one end having telescoping relation with said tubular body, means coacting between said sleeve and body for selectively axially displacing said sleeve and body with respect to each other, and work-supporting means at the other end of said sleeve, said work-supporting means comprising aligned concave surfaces facing axially outwardly and away from said tool on an alignment axis extending transverse to the path of axial movement of said rotating part with respect to said sleeve as said displacement means is operated, and releasable clamp means carried by said sleeve and engageable over an elongate workpiece to secure the workpiece against said surfaces and in said path of movement. 

1. A fixture for holding a tool and workpiece in operative relationship with one another, comprising a tubular workpiece and tool holder having a bore extending therethrough along the tubular axis and having at one axial end a workpiece-receiving slot cut along an axial plane and bottoming at a desired axial location to define opposing workpiece-retaining jaws at the slot bottom, said slot being sized to receive and place a workpiece across the bore between the jaws near the bottom of the slot, said holder further having at the other axial end a tool-guiding slot extending along the holder and bottoming at a desired axial location from the other holder end, said tool-guiding slot having a sufficient axial length for guidance of a tool placed within the bore into operative engagement with the workpiece across the bore, and means for retaining the workpiece into firm engagement with the bottom of the slot.
 2. The fixture of claim 1, wherein said workpiece receiving slot bottom is selectively shaped with said jaws converging towards one another at the axial plane, with said workpiece being retained against the converging jaw portions to hold said workpiece symmetrically with respect to the axial plane.
 3. The fixture of claim 1, wherein said last-defined means includes a nut threadedly engaged to said tubular holder at the workpiece-receiving end.
 4. The fixture of claim 1, wherein said holder includes telescoping inner and outer tubular members at the tool-holder end, key means coacting between said members to limit their relative movement to substantially that of axial displacement, and feed means including rotatable member threaded to one of said tubular members and in longitudinally located relation to the other of said tubular members.
 5. A fixture for determining the operative relationship between a tool and workpiece, comprising a tubular workpiece engaging and tool holding means having a bore along the tubular axis and externally threaded, the bore of said tubular means at one end being adapted for concentric guided support upon a nonrotating tubular end of a tool, said tubular means at said end having an elongated key slot for keying the same against rotation with respect to said tubular end of the tool, nut means threaded to said tool holder at the slot region and including means for longitudinally locating the same with respect to said tubular end of the tool, whereby nut rotation adjustably positions the tubular holder with respect to the tool, and work-engaging means at the otHer end of said tubular means and including a circumferentially continuous member in threaded engagement with said tubular means at said other end.
 6. The fixture of claim 5, in which said other end of said tubular means is longitudinally slotted to receive a workpiece, and in which said circumferentially continuous member is a nut engageable with an inserted workpiece to drive the same into tight seating against the inner slotted limit.
 7. The fixture of claim 5, in which said circumferentially continuous member is a cap having a threaded bore engaged to threads at said other end of said tubular means, said cap having a central opening at the closed end thereof for reception of a tool element held by said tool.
 8. A fixture for determining the operative relationship between a rotary tool and a workpiece, said tool having a rotatable part projecting from a nonrotating part, comprising a tubular body having means at one end for removable attachment to the nonrotatable part of the tool and with the rotatable part projecting within the bore of said body, a sleeve at one end having telescoping relation with said tubular body, means coacting between said sleeve and body for selectively axially displacing said sleeve and body with respect to each other, and work-supporting means at the other end of said sleeve, said work-supporting means comprising aligned concave surfaces facing axially outwardly and away from said tool on an alignment axis extending transverse to the path of axial movement of said rotating part with respect to said sleeve as said displacement means is operated, and releasable clamp means carried by said sleeve and engageable over an elongate workpiece to secure the workpiece against said surfaces and in said path of movement. 